Minna Tallqvist*

ABSTRACT: Burial in sediment-dwelling clams is affected by morphological features, such as shell shape and size, but also by biotic and abiotic factors, such as predator presence, oxygen deficiency and sediment characteristics. In the Baltic Sea, oxygen
deficiency is a severe problem not only in the deep basins, but also in the shallow coastal areas, due to eutrophication. In the species-poor Baltic Sea, the bivalve Macoma balthica (L.) is a key species in both shallow and deep bottoms. This paper
analyzes the impact of biotic and abiotic factors on the burrowing behaviour of M. balthica. Experiments were conducted to study the importance of sediment type, hypoxia, predator presence and algal mats on the burrowing behaviour (start of burial
and burial velocity) of M. balthica. Results show that sediment type and the presence of the predatory isopod Saduria entomon did not affect the burrowing behaviour of M. balthica. In contrast, the burrowing behaviour was negatively
influenced by hypoxia and drifting algae. Physical disturbance and oxygen decifiency are important forces that may displace M. balthica in the sediment and make it susceptible to predators at the sediment surface. Burial in the sediment is the only
way in which infauna bivalves may escape predators, and this study shows that burrowing capability can be affected by poor environmental conditions.